As a cathode ray tube, there has been proposed a color cathode ray tube having a so-called black-matrix phosphor screen which is formed by filling a light absorbance property layer, for example, a carbon layer between respective color phosphor layers in order to improve the contrast. Generally, such black matrix phosphor screen is formed as follows. In this example, each phosphor layer is formed as a stripe shape. In the first place, a PVA (polyvinyl alcohol) photo-sensitive film is coated on the inner surface of a face plate of a cathode ray tube. This photo-sensitive film coated is exposed three times in response to red, green and blue colors by using the same exposing mask and then developed, thus a PVA stripe being formed. Then, after the carbon film is formed on the entire surface of the inner surface including the PVA stripe, the PVA stripe is dissolved, removed and a carbon stripe is formed on the portion corresponding to the portion between the PVA stripes. Next, a green phosphor slurry, for example, is coated on the entire surface of the inner surface, exposed via the exposing mask and developed to thereby form the green phosphor stripe. In like manner, a red phosphor stripe and a blue phosphor strip are formed hereinafter and thus the black matrix phosphor screen is formed.
By the way, as the cathode ray tube is arranged to become more and more high-definition one recently, it is requested to make the PVA photo-sensitive film thinner in order to obtain a thin carbon stripe whose side edge is sharp (so-called sharp edge). As a result, when the carbon film is thin, even if the PVA stripe is dissolved, the carbon film remains in the uncessary portion, obstructing the good carbon stripe from being obtained. Accordingly, unless the film thickness of the carbon film is made thin to such an extent that it can be peeled off by dissolving the thin PVA stripe, it is not possible to obtain the thin carbon stripe of which the side edge is sharp. However, the thin carbon stripe thus formed is burned through the succeeding baking process and then becomes white. In consequence, in the prior art, the carbon film can not be made thin to such extent that the good stripe can be obtained. Hence, it is difficult to obtain particularly a high definition black matrix phosphor screen.
In view of the above mentioned aspect, this invention is to provide a cathode ray tube in which the black matrix phosphor screen of high definition can be formed.